People who suffer from gout have long believed that eating tomatoes can trigger a flare-up of the painful disease, and a new study from New Zealand's University of Otago found a biological basis for their belief.

Gout is a painful form of arthritis that often attacks the big toe, causing severe pain, redness, and tenderness. Once called the "disease of kings" because of its link with rich food, more than 8 million American adults have gout, and 3.9 million have been diagnosed at some point. According to a study published in Arthritis & Rheumatism, gout affects almost three times as many men as women.

Once a person has gout, particular foods can trigger a gout attack. Otago researchers noticed that gout patients rated tomatoes as the fourth food most likely to trigger gout, believing that only seafood, alcohol, and red meat were worse.

"We thought it important to find a biological reason for this to add weight to what gout patients are already saying," said researcher Tanya Flynn.

After determining tomatoes are a commonly cited trigger food, the authors analyzed data from 12,720 male and female patients in three U.S. studies. The data showed that eating tomatoes was linked to higher levels of uric acid in the blood, which is the major cause of gout.

Flynn says that while their research was not designed to prove that tomatoes trigger gout attacks, it suggests that they can raise uric acid levels to a degree comparable to other commonly accepted gout trigger foods, such as seafood.

"We found that the positive association between eating tomatoes and uric acid levels was on a par with that of consuming seafood, red meat, alcohol or sugar-sweetened drinks," she said.

Flynn noted that the most important thing that people with gout can do to prevent attacks is take a drug, such as Allopurinol, to reduce uric acid levels.

"Avoiding tomatoes may be helpful for people who have experienced a gout attack after eating them, but with proper treatment this doesn’t have to be a long-term avoidance," she said.

The study is published in the journal BMC Musculoskeletal Disorders.